Current televisions or communication products retrieve transmission signals from carriers. Therefore, a receiving end needs to generate an extremely precise local oscillation signal or a clock signal for demodulating the carriers. In addition, for the clock signal, precision is required not only in frequency, but also in phase.
Conventionally, a phase-locked loop (PLL) is capable of generating an original clock signal having a same frequency as that of a reference signal. However, a phase of the original signal may differ from a desired phase. To obtain a clock signal with precision in both phase and frequency, an adjustment on the phase of the original clock signal may be required.